1. Technical Field of the Invention
The present invention relates to a novel notched-fed antenna which features a smaller size with respect to prior art antennas, a multifrequency behavior or a combination of both effects.
The radiating element of the novel notched-fed antenna consist of a polygonal, multilevel or loaded shape and a set of notches inserted next to the feeding zone of said polygonal, multilevel structures or loaded shapes.
The invention refers to a new type of notched-fed antenna which is mainly suitable for mobile communications or in general to any other application where a compact, small or multiband antenna is required.
2. Description of Related Art
The growth of the telecommunication sector, and in particular, the expansion of personal mobile communication systems are driving the engineering efforts to develop multiservice (multifrequency) and compact systems which require multifrequency and small antennas. Therefore, the use of a multisystem small antenna, which provides coverage of the maximum number of services, is nowadays of notable interest since it permits telecom operators to reduce their costs and to minimize the environmental impact.
A variety of techniques used to reduce the size of the antennas can be found in the prior art. A. G. Kandoian (A. G. Kandoian, “Three new antenna types and their applications, Proc. IRE, vol. 34, pp. 70W-75W, February 1946) introduced the concept of loaded antennas and demonstrated how the length of a quarter wavelength monopole can be reduced by adding a conductive disk at the top of the radiator. Other top-loaded antennas were introduced by Goubau, as it is illustrated in U.S. Pat. No. 3,967,276, or described in U.S. Pat. No. 5,847,682 entitled “Top loaded triangular printed antenna”. However, in all these prior art solutions the basis of the mechanism of how the antenna size is reduced can be found in the capacitive component introduced by the addition of the loading structure at the top of the radiating element. In contrast, the present invention discloses a new mechanism for reducing the antenna size and obtain a multiband behavior.
J. McLean (“Broadband, robust, low profile monopole incorporating top loading, dielectric loading, and a distributed capacitive feed mechanism”, Antennas and Propagation Society, 1999. IEEE International Symposium 1999, vol. 3, pp. 1562-1565) describes a top-loaded antenna which includes a capacitive feed.
Some previously reported dual-band antennas use a spur line filter which may be partially similar in shape to the present invention. However, this previous solution is used for patch antennas, which have both, a configuration and radiation mechanism, different from a monopole or dipole antenna, which are considered in the present invention.
Two other different alternatives to achieve an antenna with a multiband and/or small size performance are multilevel antennas, Patent WO0122528 entitled “Multilevel Antennas”, and miniature space-filling antennas, Patent WO0154225 entitled “Space-filling miniature antennas”.